Aircraft include many parts that are suitable for monitoring and periodic replacement. For example, many aircraft braking systems include one or more servo valves suited for converting variations in an electrical signal into variations in how much hydraulic fluid is transmitted to a brake actuator. Such servo valves can be used to control powerful hydraulic cylinders with small electrical signals. They can provide precise levels of control over force, position, pressure, and velocity, etc., such as by electrically coupling to a power source to apply a desired amount of electrical current to the servo valve in order to actuate a poppet internal to the servo valve and suitably open or close the servo valve to thus control the amount of hydraulic pressure output by the servo valve. Sensors in communication with servo valves can monitor the amount of electrical current (electrical signal) input into the servo valve and the corresponding hydraulic pressure output from the servo valve (hydraulic pressure signal).
Typically, transport aircraft utilize antiskid systems to control wheel skidding during braking. Uncontrolled skids, or “lockups” may result in greatly reduced braking effectiveness, loss of tire cornering (“road-holding”) capability, and tire flatspots or blowouts. During most braking conditions, this skid protection is achieved by circuits or mechanisms which release braking pressure, via the servo valve(s), to a single (or group of) wheel(s) upon detection of a sudden decrease in wheel speed. Servo valves comprise relatively tortuous paths through which the hydraulic fluid travels in order to release the braking pressure.